In order to de-constructing constructions, such as buildings or bridges made of reinforced concrete, it is common to use a breaking machine or breaker which is adapted to be attached to a forward end of a drive arm of a working machine, such as power shovel. One example of such breaking machines is known, as disclosed In Japanese Patent Public Disclosure No. 02(1990)-232470, which comprises a pair of movable arms pivotably attached, at the intermediate portions thereof, to a support frame, and a hydraulic cylinder connected to the rearward end of each of the pair of movable arms. When the hydraulic cylinder Is actuated to be extended or retracted, the pair of movable arms are rotated to be closed or opened so as to clamp at the forward ends thereof a concrete material therebetween.
It is noted that various operations, such as crushing of concrete material, secondary crushing of such concrete material, and shearing of steel bars or steel frames, are involved In deconstruction work for construction, such as buildings of reinforced concrete, or bridges. It should be noted, however, that such various operations could not be performed by a single breaking machine of prior art as mentioned above. Thus, it is necessary, according to prior art, to provide a plurality of shearing machines or breaking machines suitable for individual operations, such as shearing of steel bars or steel frame, crushing of concrete material, or secondary crushing of such concrete material, so that a particular breaking machine or crushing machine may be selectively attached to the tip of a drive arm of a working machine, depending upon particular operation. In this regard, it should be noted that replacement of such breaking machine or crushing machine is time-consuming, and thus, efficient and quick de-construction work cannot be expected.
It is also noted that play or backlash may be created between the pair of movable arms after prolonged use thereof, so that steel bars or steel frames cannot be sheared accurately. Such play is caused from abrasion or wear of the slide surface of the movable arms, opposite to the surface on which the cutter is attached, and the surface of tile support frame in slidable engagement of the slide surface of the movable arms, due to a force component, generated upon shearing of steel bars or steel frames, in the direction perpendicular to the direction in which the movable arms are opened and closed, the force component tending to separate the pair of movable arms from one another. In such case, it is necessary for the movable arms to be repaired or replaced with new ones so as to facilitate secure shearing of steel bars or steel frames. This is disadvantageous in view of economy.